This invention relates in general to communication with optical signals and, more particularly, to a method and apparatus for effecting switching of optical signals.
Telecommunications is a field which has been rapidly evolving over the past twenty years, fueled in part by the progressively increasing popularity of technologies such as cellular telephones, facsimile machines, and computer communications that use the Internet. Due to these growing new technologies, there has been a progressively increasing demand for telecommunications equipment with greater information-carrying capacity, which in turn has created a progressively increasing focus on effecting communications through the use of optical signals.
High bandwidth fiber optic telecommunication systems are being deployed around the world. This is creating a backbone system which couples major metropolitan areas. Currently, when these existing systems need to effect switching of an optical signal, they typically convert the optical signal into an electrical signal, effect electrical switching of the electrical signal, and then convert the resulting electrical signal back into an optical signal. This greatly delays the propagation of information through the system, and is expensive because it increases the complexity of the system.
In order to avoid this problem, attempts are being made to develop optical switches which would directly switch optical signals, without temporarily converting them into electrical signals. Technologies which are being considered include micro-electro-opto-mechanical switches, bubble jets, liquid crystal arrays, moving opto-mechanical mirrors or prisms, electro-optic controlled coupled waveguides, and thermally controlled coupled waveguides. While these existing approaches have been generally satisfactory for their intended purposes, they have not been satisfactory in all respects. To some extent, these approaches involve problems such as poor reliability, high insertion or transmission losses, difficulty in scaling these switching approaches to larger sizes, and costly manufacturing techniques. Further, these existing approaches have relatively slow switching speeds, on the order of approximately a few milliseconds.
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus for processing optical signals, which avoids at least some of the problems discussed above. According to the present invention, this need is addressed by the provision of a method and apparatus for operating an optical switch which includes an input for optical radiation, an output spaced from the input, and a first region disposed optically between the input and the output. The method and apparatus involve: providing within the first region a plurality of second regions and a third region, the second regions being provided at a spaced locations within the first region, and the third region having an index of refraction and being a portion of the first region other than the second regions; subdividing the second regions into first and second groups which are mutually exclusive, the second regions of the second group being arranged along a path which extends through the first region from the input to the output and which is free of the second regions of the first group; and selectively operating the switch in first and second operational modes, wherein in the first operational mode each of the second regions has an index of refraction different from the index of refraction of the third region so that the third region and the second regions cooperate to prevent optical radiation with a predetermined wavelength from propagating within the first region, and wherein in the second operational mode each of the second regions of the first group has an index of refraction different from the index of refraction of the third region so that the third region and the second regions of the first group cooperate to prevent radiation with the predetermined wavelength from propagating within portions of the first region other than along the path, and in which each of the second regions of the second group has an index of refraction selected in relation to the index of refraction of the third region so as to permit radiation with the predetermined wavelength to propagate through the first region along the path from the input toward the output.